Smyrna 
Elementary School

The Effect of Trawling on the Estuary
Duke/Smyrna School Partnership

Conclusions 2001 Data

     The data for the summer and fall was compiled and analyzed in several different ways.  We totaled the number of animals caught in each location, as well as the total biomass (grams) in each location.  Sleepy Creek in the summer, which is an area closed to trawling, yielded the largest catch, while the Straits, an area open to trawling, yielded the smallest catch.  

     We also totaled the number of each species caught in each location.  Pinfish were the most frequently caught species in Sleepy Creek in the fall, Midden's Creek (open to trawling) in the fall, and Midden's Creek (closed to trawling) in the fall.  Shrimp was the most frequently caught species in Sleepy Creek in the summer.  Silverside, a small minnow, was the most frequently caught species in Midden's Creek (open to trawling) in the summer.  The most frequently caught species in the Straits in the summer and fall was arrow shrimp, a small inedible shrimp.

     Dr. Bill Kirby-Smith, a professor at Duke University Marine Laboratory, visited our class as a guest instructor, and taught us about analyzing data using a t-test, which analyzes the difference between two means.  First, we took part in a simulation using beans to represent two populations of fish.  We used a t-test to determine if there was a statistical difference between the two populations. 

     Next, we applied this same technique to some of our data. As a class, we asked the question whether there was a significant difference between the number of shrimp caught in Sleepy Creek in the summer, and the number of shrimp caught in Straits in the summer.  Sleepy Creek is closed to trawling, and Straits is open to trawling.  Trawling is one of the common methods used by commercial fishermen to catch shrimp.  The null hypothesis was that there is no difference.  Most of us hypothesized that more shrimp were caught in Sleepy Creek based on the numbers caught.  We were surprised when the results of the t-test showed that statistically there is no difference between the numbers of shrimp caught at each site.  The critical value for our test was 2.306.  Any number above this value would cause us to reject the null hypothesis.  Our t-value for this test was 2.23, thus we were not able to reject the null hypothesis.  In other words, statistically, there is no difference between the number of shrimp caught in Sleepy Creek and Straits.  

     We realize that it would be very difficult to answer the question, "How does trawling affect the estuaries?", however, this project has given us a glimpse of how scientists work.  There are many variables that must be controlled for when conducting a study in the natural world, and our project has not controlled for these variables.  However, this project has helped us realize that science plays an important role in helping to resolve conflicts between different groups struggling to use the same resources.